Electric-arc welding.



citizen ofthe United States,

T621 h may concern: j

"and State of New 'tain new and useful Improvements in Electhe followingto be a 'full, clear, and exact if most erratic. The resistance of anarc de- 1 .the current begins to decrease, and to lessen 'age to fall asthe-arc stream increases in MOBTONQARENDTLOE new-manna; AssmnoaroHEINRiGH 1.53. 51mm, or

nnw YORK, N Y. I immense WELDING,

I specification of Letters l'atent. l 'aj ented 20, 1915, NoD'rawin'g.jApplicationfiledDecembetY, 1914. serialnois'zseca' cross section (a e.current increases.) the a tendency for the current to approach aninfinite value can be overcome; similarly if the arc stream tends todecrease incross section '(current fall) some rise in voltage willprevent this. However, to besatisfactory, this balancing action mustnot; consume power. Furthermore, a constant current supply system willnot answer the purpose, because, while a large current flow is necessaryat striking the arc, to heat the point of contact and initlate rapidionization, yet

that' I, MORTON Annnn'r,

residing at and whose post-office address is Columbia University,borough of; Manhattan, city, county,

York, have invented cer- Beit known trio-Arc Velding; and I do herebydeclare description of the invention, such as will enable others skilledin the" art to which it appertains to make and use thesame.

My nventiom'comprises modifications in the art of electric arc welding,with the-objcct of decreasing the size of the powergenerating equipmentrequired and increasing the efficiency of the operation.- When anelectric arc is "fed directly by a constant potential system, the actionof the arc-is cut the metal to be repaired, and no metal quired atstarting is much greater than the working current value, and, ifcontinued,

idly melt the repair electrode, in metallic electrode welding. In otherwords, the maximum current onshort-circuit should be substantially lessthan would occur on a constant potential system, and should not exceedthe predetermined maximum value required for initial heating. Themaximum voltage on rupturing the arc should be much less than wouldoccur on a constant-current system and should not exceed apredeterpotential circuit has led to the general mined maximum value,which is safe for practice of introducing a steadying or balthe welderand is below the cutting voltage. ancing resistance in series with theare. I have discovered that The use of such a resistance, whileunecoditions may be attained by causing the curnomical, has been thegeneral procedure in rent variations accompanying alterations in theresistance of the arcto set up predeterthe case of electric arc welding;even though mined variations of the applied voltage in an opposite senseand of less extent than the energy consumption in the balancing rewouldbe required to maintain a constant sistance has been equal to or greaterthan the energy consumption in the arc. Thus,

generators furnishing about seventy volts current. That is to say, bymaking such provision that as the arc resistance falls the appliedelectromotive force will be reduced have been used where the voltagedrop somewhat, but not sufiiciently to prevent a across the arc was onlyabout volts, the

volts excess being used up in the balancrise of current within thepredetermined limits; and as the arc resistance rises thecreases withincrease of current, which results in a tendency for the current tobecome infinite if a constant potential 1s mai tained across itsterminals. Similarly, if

the cross-section of the arc, the resistance increases and furtherchokes of)? the current until the arc goes out. This unstablecharacteristic of the electric are on a constant ing resistance toproduce a stable arc. This drop of volts means a power loss directlyproportional to. the "current employed, which, in metallic arc welding,for example, .arpproximates 200 amperes, or a .loss of nearly 9 k. w.-out of 14 k. w. That is to say, only about.33%' of the power supplied tothe circuit is used'to produce the arc.

I have carefully studied the phenomena of the arc, and realize that ifsome means can be introduced which will cause the voltwhat, but notsufiiciently to prevent a current reduction within the predeterminedlimits.

A generator having the desired .voltagecurrent characteristic may besecured by various methods, for example: A separately excited generatormay be designed to supply about 30 volts on open circuit, while thecombined eifect of armature reactionand armacould the deposited. Thecurrent value resuch a'large current flow, if it continued as the arciselonga't'edyw'ould'rapidly melt' or:

would cut the metal to be repaired and rapthese desirable con- 1 appliedelectromotive force will rise some- 1 5 voltage of the x that a currentof about 300-350 amperes re-.

ture resistance fices to lower the terminal pressure to 25 volts, andonshort circuit, the armatu're reaction and armature drop suflice to lowerthe machineto such an extent sults. In such case quick response to thechanges of arc current would be hastened byu sing a laminated fieldstructure Another way ofaccomplishing the same result withployagenerator with field excitation produced by current from an externalsource and also by a shunt winding, the separate excitation and shuntexcitation being so proportioned that in short circuit.

failure of the shunt excitation lowers the machine voltage so that theshort circuit current will able value, while the increase of the machinevoltage on lengthening the arc is limited to a safe value through thesaturation hastened by the separate excitation. A third method is tomachine, provided with a weak difl'erential winding, suflicient to limitthe current on striking the arcto the safe starting value, or in placeof the differential winding, a machine provided with interpoles may beem- 3 ployed and the differential result accomplished by shifting thebrushes slightly from the neutral position. I have listed severalcontrol methods, though others exist in the drop at working currentsufout exaggerated armature reaction, is to emthe not rise to an,obj'ectionuse a separately excited the instant of art, and are known toanycompetent designing engineer.

- In practising this method of welding,

about .400 amperes. -This'large value of cur- .rent on short circuitexisted only durin the moments of starting the'arc and the Voltageacross the are at the moment of incepwhen operating with an arc currentbeon short circuit the current was" tion was of such low value-thatburning of;

structure did not result.

atIclaim is: p p

The method of electric arc welding or repairing which consists instriking the are between an electrode and the metal to be repairedandcausing current variations accompa'nying alterations-in theresistance of the arc to vary the voltage applied to the circuit in theopposite sense and to an extent substantially less than would. berequired to maintain a constant current, whereby the large initialheating current which flows at striking the arcis reduced and maintainedas a steady working current.

In testimon whereof I afiix my signature, in presence 0 two witnesses.

MORTON ARENDT. Witnessesz WILLIAM'H. DAVIS, M. A. BILL.

